This invention relates to instruments for measuring the flow velocity and/or the volumetric through-flow of fluids in conduits such as pipelines.
Today's flow-through measurement processes use amongst others ultrasound counters for measuring the through-flow. In general, this involves placing a flow meter with appropriate connecting flanges into a segment of a pipeline. The flow meter has ultrasound converters, or ultrasound probes, which are mounted in a tubular section of the flow meter. A signal processing unit is provided for controlling the ultrasound probes and processing signals generated by the probes.
This technique measures a difference in the travel time (from emission to receipt) of two ultrasound signals which are emitted in one direction and then returned and have a component in the flow direction of the fluid through the flow meter, and another component in the opposite direction. It is necessary that the signals are emitted and received at an angle other than 90° to the flow direction.
All ultrasound counters have the common characteristic that the probes extend at an oblique angle from an otherwise tubular, round body of the flow meter. Each probe requires an electric connection with a signal processing unit. Accordingly, one or more cables that necessarily protrude from each probe are essentially unprotected all the way to the signal processor. To protect against explosion dangers, the cables are partially encased in separate tubes that are mounted to the flow meter.
Flow meters, such as the above-mentioned ultrasound counters, are used in rough industrial environments, for example in the chemical industry, at natural gas wells, at filling stations, or on transmission lines. In such environments, the flow meters, which, depending on their diameter, can be very heavy, must be handled with heavy equipment such as fork lifts and the like.
Such rough handling creates the danger of damaging or severing unprotected cables during installation, inspection or maintenance. As a result, the counters are often installed without cables. This renders the flow meter and its flanges more accessible and reduces the danger of downtimes due to damaged or severed cables. However, it significantly increases the installation time and effort and the costs associated therewith.